It has been generally accepted that the fungicidal activity of alkyl guanidines and their salts depends on the chain length of the N-alkyl group, i.e. 10 to 20 carbon atoms (Kirk-Othmer Encyclopedia of Chemical Technology, 2nd Edition, Volume 10, page 225). However, these higher molecular weight amino groups cause the compounds to be highly insoluble in water and thereby complicate their use as aqueous sprays and treating solutions. The long carbon chain on the nitrogen also prevents penetration of the amino or guanidinyl moiety into plant tissue and thus hinders systemic activity. Accordingly, the activity of these compounds is of short duration and protection over an extended period requires a high replacement ratio.
The salts of alkylguanidines for the control of certain fungi are disclosed in U.S. Pat. Nos. 3,142,615 and 2,867,562. These compounds are highly selective to non-mutated forms of tree fungi; however, against the certain mutated and more resistant forms which are currently most troublesome, the alkyl guanidines and their salts show little or no fungicidal efficacy. Also because of their moderately phytotoxic affect, the dosage levels of these compounds in the fungicidal composition cannot be appreciably increased. Accordingly, use of these fungicides has been restricted to the hardier woody plants.
The alkoxyphenylaceto guanidines of U.S. Pat. No. 2,734,904 and the phenylamino guanidines of U.S. Pat. Nos. 3,794,685; 3,821,406 and 3,996,232 are purported to have certain pharmaceutical uses; however, these disclosures fail to suggest any fungicidal use or properties for the compounds set forth therein.
The formation of thermosetting resins by conversion of aliphatic acyl guanidines to guanamines is the subject of U.S. Pat. No. 2,408,694. Also, U.S. Pat. No. 2,378,724 relates to the types of coating and textile finishing composition containing aliphatic acylguanidines which provide water-proofing to the treated fabric. Certain other guanidines of U.S. Pat. No. 2,545,423 are used as barrier coatings to prevent dye diffusion. However, these patents also fail to suggest any mycological inhibition.
According to U.S. Pat. No. 3,759,991, carbamylated guanidines are found to be moderately effective fungicides; however, unusually high concentration of these compounds is required to bring about results. Unfortunately, these compounds also inhibit plant growth and cause stunting and abscission of new growth, which characteristics have prevented wide acceptance as fungicidal agricultural aids. The cyano-, aminol-, and carbazone-guanidines of U.S. Pat. Nos. 3,564,607; 3,564,608; 3,632,333 and 4,099,956 function only as herbicides and display no fungicidal properties whatever. Certain biguanides of the type disclosed in U.S. Pat. No. 3,222,398 possess limited fungicidal properties with selectivity to a specific fungus infection; but these moderately toxic compounds have only a narrow spectrum of efficacy. Finally the aliphatic guanidine xanthates of U.S. Pat. No. 2,198,774 while active fungicides, are highly toxic and therefore not suitable for use on crops.
Accordingly, it is an object of the present invention to overcome the above deficiencies and to provide fungicides which are innocuous to plant, animal or human contact;
Another object is to provide a fungicide of the guanidine type having better penetration of plant tissue;
Still another object is to provide a fungicide effective on a variety of fungi at low dosage levels;
Another object is to provide a guanidine which possess fungicidal activity for an extended duration;
Yet another object is to provide an economical and efficient process for the reduction, elimination or prevention of fungus infection in a plant, plant part or soil.